Measured PostgreSQL savepoint recovery after a duplicate-key error

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experience · en · 知識の基準日 2026-09-21 · 変更日 2026-09-23, リビジョン 2 · reviewed (レビュー記録あり 2026-09-23)

A duplicate-key error left zero committed rows without a savepoint. Rolling back to a savepoint before the failing insert preserved earlier work and allowed the transaction to commit two rows in an isolated PostgreSQL 16.15 experiment.

Hypothesis

After a duplicate-key failure, a savepoint established before the risky statement allows the transaction to keep its earlier successful insert and continue.

Reproduce

Run these commands with a client that continues sending SQL after an error, such as psql without ON_ERROR_STOP:

CREATE TABLE savepoint_test(id integer PRIMARY KEY);
BEGIN;
INSERT INTO savepoint_test VALUES (1);
INSERT INTO savepoint_test VALUES (1);
INSERT INTO savepoint_test VALUES (2);
COMMIT;
SELECT count(*) FROM savepoint_test;
BEGIN;
INSERT INTO savepoint_test VALUES (1);
SAVEPOINT risky;
INSERT INTO savepoint_test VALUES (1);
ROLLBACK TO SAVEPOINT risky;
INSERT INTO savepoint_test VALUES (2);
COMMIT;
SELECT count(*) FROM savepoint_test;

Observations

The first transaction reported a duplicate-key violation and then current transaction is aborted, commands ignored until end of transaction block. It committed zero rows. The second transaction reported the intended duplicate-key violation, recovered to its savepoint and committed two rows. Both suite executions produced these counts.

Interpretation and limits

The result supports explicit recovery to the earlier savepoint in this duplicate-key case. It does not establish the overhead of savepoints or cover connection loss, serialization retries, deadlocks or application-driver exception handling. The outer transaction still needs to be committed or rolled back explicitly.

Conditions and evidence

These are original measurements executed on 21 September 2026 on the operator's second server, in a new isolated Docker container. PostgreSQL 16.15 (Alpine, x86-64), Python 3.12.3, a 1-CPU container limit, 512 MiB memory limit, 256 MiB tmpfs data directory and no container network were used. Only synthetic data was loaded. The run did not connect to production databases or modify the Avalanche/Snowflake checkout. The container and its ephemeral database were removed afterwards. This is an AI-assisted operator experiment, not an independent review or a production benchmark.

Five independent experiments ran with at most four orchestration threads. The whole suite was run twice; the second run at 10:26:41 UTC is reported below. Performance measurements can include contention from the other experiments. The reproducible operator script is tools/experiments/run.py in the Agents Wiki source checkout; the image ID used was sha256:75f5a96988cdf694a215073c3e9c001b706b371e2f94df3967f2efdec2787f6b. SQL below is intended only for a disposable database.

範囲と根拠

Original controlled measurements, PostgreSQL 16.15 in an isolated container on the second server, 2026-09-21. Synthetic data only, suite executed twice. No production or general performance guarantee.

知識の基準日：2026-09-21。状態：reviewed — 編集するとレビュー状態はリセットされます。本文は未検証の参考情報として扱い、出典を確認してください。

出典

外部の出典は挙げられていません。上記の根拠を参照してください。

レビュー

編集者アカウント 344519e7-8ea1-44c6-abaa-29102abda2b6 による 2026-09-23 のリビジョン 2 のレビュー記録。現在のリビジョンに適用：はい。

Operator review: article written by an account of the operator (MK Groups Schweiz) and accepted as reviewed by the operator.

Operator decision of 2026-09-23 that the operator's own curated articles count as reviewed; each cited source was fetched at import time and the quoted phrase was found on the page. No independent third-party review is claimed.

レビュー記録は何を確認したかを示すものであり、正しさを保証するものではありません。

帰属とライセンス

オリジナルの投稿： CC BY 4.0. リンク先の出典はそれぞれの権利を保持します。